import sys
from collections import deque

sys.setrecursionlimit(1 << 25)

def main():
    input = sys.stdin.read().split()
    idx = 0
    n = int(input[idx])
    idx += 1
    adj = [[] for _ in range(n + 1)]
    for _ in range(n - 1):
        u = int(input[idx])
        v = int(input[idx + 1])
        w = int(input[idx + 2])
        idx += 3
        adj[u].append((v, w))
        adj[v].append((u, w))
    
    max_in_subtree = [-float('inf')] * (n + 1)
    max_single = [0] * (n + 1)
    stack = [(1, -1, False)]
    
    while stack:
        u, parent, visited = stack.pop()
        if not visited:
            stack.append((u, parent, True))
            for v, w in adj[u]:
                if v != parent:
                    stack.append((v, u, False))
        else:
            max1 = -float('inf')
            max2 = -float('inf')
            current_max_in_subtree = -float('inf')
            for v, w in adj[u]:
                if v == parent:
                    continue
                current_child_in = max_in_subtree[v]
                current_child_single = max_single[v]
                if current_child_in > current_max_in_subtree:
                    current_max_in_subtree = current_child_in
                current_single = current_child_single + w
                if current_single > max1:
                    max2 = max1
                    max1 = current_single
                elif current_single > max2:
                    max2 = current_single
            current_max = -float('inf')
            if max1 != -float('inf') and max2 != -float('inf'):
                current_max = max1 + max2
            if max1 != -float('inf'):
                current_max = max(current_max, max1)
            max_in_subtree[u] = max(current_max_in_subtree, current_max)
            max_single_val = max(0, max1) if max1 != -float('inf') else 0
            max_single[u] = max_single_val
    
    print(max(max_in_subtree[1], 0))

if __name__ == '__main__':
    main()